bigger is better but weights more
but wow, 10 years. We get about 4-5 here in the US, BMW or aftermarket. If the batteries are the same size, the plates could be thinner in the larger one, or maybe it's just supply versus demand, with most folks buying the original 65ah spec.
Odd thing is it turning over slower when hot though... Usually, there's more residual pressure from the fuel pump when hot, less resistance to turn since everything has had oil pressure more recently, etc.
Most alternators run about 13.8 at the battery, Bentley manual quick-check says 12.6v engine off, ~ 14v running (between 13.5-14.5 depending on temp, conditions).
Re: bigger is better but weights more
My first BMW was an E36 318is Sept 92, the battery in it lasted till May 2001 from memory, when I "cooked" it doing a 400Km freeway trip. The close to 9 years running made me buy another BMW battery for it (plus it was cheaper than an aftermarket one at the time).
My other car a 97 E39 528i had it's battery replaced in 2007, so that is 10 years of life. It has a bigger capacity and current rating so that's why I think it got more years out of it, it is able to supply the current loads with less stress on its internals.
Also temperature plays a part I guess in the chemistry of batteries and their cycle life or longevity, Australia is pretty warm all year round.
But I'm stumped; capacity versus price? But the CCA and RC figures that are written on the BMW batteries will be the decision making figures for me. The BMW Customer Service girl is waiting on the Technical Team to get out of a meeting (long meeting), so I asked her to get the storeman to take a photo of the battery labels and email them to me - I just want to know what I'm buying and why, but it all seems to be too hard to get the answers.
61218381714 versus 61218381745
Well these are the part numbers from BMW, and it looks like the prices are based on "apples and oranges".
The 65Ah (61218381714) for AUS$280 is labelled as "filled" on all the databases
The 75Ah (61218381745) for AUS$230 is labelled as "empty"
So BMW may have added the acid and filling labour charge to the cost of the 65Ah filled battery, and don't seem to want to charge extra money for the 75Ah filling (61218381744)- WOW
So I've ordered the 75Ah one from my Indy guy, he already said to me that it is empty so his cheaper price includes the filling and battery charging. I eventually got an answer from the BMW Dealer, not BMW Australia, on the CCA values; 300A for the 65Ah, 380A for the 75Ah (seems low, they may be quoting the CA value). I'll have a look when I see the battery label.
61218381745 Empty - but not any more
Battery is in and all feels good. The BMW battery is bigger than the old "no name" one so I'll hopefully get another decade of life out of it. The old battery shat out sulphate or whatever the chalky crap is again so it was well on its way out - it is now. The battery pan is cleaned up and primed again with battery terminal paint, some rust was appearing on the battery holder.
From the label the CCA is 630A so I don't know where the Dealer guy's 380A came from or what it is. The reserve capacity is also 2 hours and 10 minutes of 25 Amps at 80degF, that should be plenty for an overnight or two.
been away a few days.... I'd suppose the
and cost to fill and charge the higher capacity battery, but you found someone willing to do it and keep the cost down, good deal!
That's great batteries last so long. You can tell in winter that cars turn over slower when cold; guess I never realized how much wear and tear that causes on battery life!